Syringe Infusion Pump

ABSTRACT

One embodiment of the present patent application is a syringe infusion pump that includes a syringe, a syringe barrel holder, and a force sensor. The syringe includes a barrel and a plunger. The plunger has a plunger axis and the barrel has a barrel axis and a barrel diameter. The syringe is one of a plurality of syringes, each having a different barrel diameter. The force sensor is positioned for detecting a force along the barrel axis. The syringe holder provides the barrel axis automatically aligned with the force sensor for each syringe of the plurality of syringes.

RELATED APPLICATION DATA

This application is a continuation of U.S. Nonprovisional Patent Application Ser. No. 12/157,477, filed Jun. 11, 2008, entitled Syringe Infusion Pump, that claims the benefit of priority of U.S. Provisional Patent Application Ser. No. 60/934,236, filed Jun. 11, 2007, and titled Axially Centered Syringe Infusion Pump Drive Mechanism, which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to the field of infusion pumps. In particular, the present invention is directed to a drive mechanism for a syringe infusion pump.

BACKGROUND

Infusion pumps currently present in the market consist of two basic types, syringe infusion pumps and volumetric infusion pumps. Typically, syringe infusion pumps accept a range of syringe sizes, typically from 1 cc to 60 cc or more in volume from a variety of syringe manufacturers. Typically these devices use a motor under control of a microprocessor. A motor such as is available from Maxon Precision Motors, Inc., Fall River, Mass., can be used. The motor is connected to a lead screw which advances a pushing element that pushes against the plunger of the syringe, driving it into the barrel of the syringe, thus dispensing fluid or other material. The devices have used sensors for determining the size of syringe loaded, the position of the plunger within its travel, whether the plunger is captured by the pushing element, and the driving force needed to push the plunger. The devices have also included encoders or other means for determining the motor speed.

The syringe drives have fixed the barrel of the syringe against a fixture, such as a V-block. A spring loaded clamp mechanism has been used to capture the barrel of the syringe against the V-block. Because the barrel diameter of a 1 cc syringe is significantly smaller than the barrel diameter of a 60 cc syringe, the pushing element has not always pushed along the center line of the syringe, and the variance between pushing element and syringe center line can be as much as 1 inch or more. The variance in the syringe center line with respect to the pushing surface has caused difficulties in measuring the force applied to the syringe which is used to estimate fluid pressure within the syringe. The variance has also caused inaccuracy in the resultant flow rate because the syringe plunger has not been driven into the syringe barrel squarely. Thus better schemes for mounting a syringe and driving its plunger are needed to eliminate these problems, and these schemes are provided by this patent application.

SUMMARY OF THE DISCLOSURE

In one implementation, the present disclosure is directed to a syringe infusion pump for use with a plurality of different size syringes, each different size syringe having a different syringe barrel diameter, and each of the plurality of syringes including a plunger having a plunger axis received in the barrel along a barrel axis. The pump includes a drive head including a force sensor positioned to sense force applied to the plunger by the drive head, the force sensor having a center; and a syringe barrel holder configured to hold each of the syringe barrels of different diameters in a fixed position with the barrel axis aligned with the force sensor center for each different diameter syringe barrel.

In another implementation, the present disclosure is directed to a syringe infusion pump for use with a plurality of different size syringes, each different size syringe having a different syringe barrel diameter, and each of the plurality of syringes including a plunger having a plunger axis received in the syringe barrel along a barrel axis. The pump includes a drive head configured to apply force to the plunger to operate the syringe, the drive head including a force sensor positioned to sense force applied to the plunger by the drive head, the force sensor having a center; a syringe barrel holder comprising a barrel clamp including a first clamp element and a second clamp element, the first and second clamp elements being movable to engage and hold syringe barrels of different diameters in a fixed position with the barrel axis automatically aligned with the force sensor center independent of the diameter of the barrel for each different diameter syringe barrel; and a syringe plunger holder mounted on the drive head comprising front and rear plunger clamps cooperating to automatically position the plunger with the plunger axis in alignment with the force sensor center, and with the plunger axis in alignment with the barrel axis independent of the diameter of the barrel of a syringe held in the barrel holder for each different diameter syringe barrel.

In still another implementation, the present disclosure is directed to a syringe infusion pump for use with a plurality of different size syringes, each different size syringe having a different syringe barrel diameter, and each of the plurality of syringes including a plunger with a plunger flange having a plunger axis received in the barrel along a barrel axis. The pump includes a drive head positioned and configured to push the plunger into the syringe barrel for each different size syringe, the drive head including a force sensor configured to sense force applied to the plunger by the drive head, the force sensor having a center; a syringe plunger holder configured and dimensioned to engage the plunger of each different size syringe with the plunger axis aligned with the force sensor center for each the different size syringe; and a syringe barrel holder configured to hold each of the syringe barrels of different diameters in a fixed position when the drive head pushes the plunger into the syringe barrel.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, the drawings show aspects of one or more embodiments of the invention. However, it should be understood that the present invention is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:

FIG. 1 is a three dimensional view of one embodiment of a syringe infusion pump of the present patent application;

FIG. 2 is a three dimensional view of a drive head, motor, and position sensing mechanism of the syringe infusion pump of FIG. 1;

FIGS. 3 a-3 c are three dimensional cutaway views of a portion of the drive head of FIG. 2 showing a plunger in position in front of a force sensor, and showing plunger clamp elements maintaining the plunger axis in front of the center of the force sensor;

FIG. 4 is another three dimensional view of the drive head of FIG. 2;

FIG. 5 is a block diagram of electronic components for the syringe infusion pump;

FIGS. 6 a-6 d are three dimensional views of the barrel holder portion of the syringe holder of FIG. 1 showing how the axis of the barrel is maintained in the same position regardless of the diameter of the barrel; and

FIG. 7 is another three dimensional view of the barrel holder portion of the syringe holder of FIGS. 6 a-6 d.

DETAILED DESCRIPTION

One embodiment of the present patent application provides a syringe infusion pump with a force sensor and a syringe holder. In this embodiment the syringe holder includes a syringe plunger holder and a syringe barrel holder. The syringe holder can include mechanisms that provide the syringe plunger axis and the syringe barrel axis automatically aligned with the force sensor for all sized syringes.

Syringe infusion pump 20 includes drive head 22, syringe barrel holder 24, motor 26, lead screw 28, and position sensing device 30, as shown in FIGS. 1 and 2.

Motor 26 turns lead screw 28 clockwise or counterclockwise to move drive head 22 toward or away from syringe barrel holder 24. Drive head 22 includes force sensor 32 against which plunger 36 of syringe 38 is positioned, as shown in FIGS. 3 a-3 c. Force sensor 32 can be one available from Strain Measurement Devices, Meriden, Conn. Plunger 36 is held in position against force sensor 32 by syringe plunger holder and syringe plunger flange holder 40 that includes front plunger clamp element 42 a and rear plunger clamp element 42 b. Plunger clamp elements 42 a, 42 b have V-grooves 44 a, 44 b that both hold plunger 36 and capture plunger flange 46. Thus, plunger axis 54 extends directly into center 56 of force sensor 32, as shown in FIGS. 3 a-3 c and FIG. 4.

Plunger clamp elements 42 a, 42 b are connected to gear 48 through racks 50 a, 50 b so that plunger clamp elements 42 a, 42 b are constrained to move equal distances in opposite directions to each other, maintaining plunger flange 46 centered before force sensor 32 and maintaining plunger axis 54 of plunger 36 extending directly into center 56 of force sensor 32, regardless of the diameter of plunger 36. Gear 48, racks 50 a, 50 b are included in drive head housing 58. One embodiment has a first plunger flange holder drive member that includes rack 50 a and a second plunger flange holder drive member that includes rack 50 b.

Post 60 holds spring 62 for providing pressure for restoring plunger clamp elements 42 a, 42 b toward each other, as shown in FIG. 4.

Force sensor 32 senses the force being applied to plunger 36 by drive head 22. Force sensor 32 is connected to motor processor 64 on electronic circuit board 66. Motor 26, barrel sensor 76, and position sensor 78 are also connected to motor processor 64 on electronic circuit board 66. Motor processor 64 can be one available from Microchip Technology Inc., Chandler, Ariz. Barrel sensor 76 and position sensor 78 can be ones available from US Digital, Inc., Vancouver, Wash. Electronic circuit board 66 also includes main microprocessor 68. Keypad 70, display 72, and battery 74 are connected to main microprocessor 68. Main processor 68 and display 72 can be ones available from Sharp Electronics Corporation, Romeoville, Ill.

Motor processor 64 controls speed of motor 26 in a software closed control loop by monitoring two quadrature signals emitted by a motor encoder that is part of motor 26. Motor processor 64 monitors output of force sensor 32 and provides an alarm signal to alarm 79 if a preset force above a threshold is detected. This force translates to a resultant fluid pressure based upon the cross sectional area of syringe barrel 96. Motor processor 64 also monitors barrel sensor 76 and determines its outer diameter and thence its volume based upon a software look up table that cross references barrel diameter to syringe barrel volume. Motor processer 64 also monitors position sensor 78 and from this position determines the state of fill of syringe barrel 96 installed.

Main processor 68 sends the display information to display 72 to be visually communicated to the user. Main processor 68 also monitors keypad 70 to enable the user to control the device via key press.

Battery 74 supplies power to all the electronics and motor 26.

Position of drive head 22 along lead screw 28 is measured with position sensing device 30, as shown in FIGS. 1 and 2. Position sensing device 30 includes guide rod 80 and position sensor 78. Guide rod 80 has helical groove 84. Pin 86 extends from drive head 22 into helical groove 84 and causes guide rod 80 to rotate as drive head 22 moves under control of lead screw 28 and motor 26. Because helical groove 84 extends only once around guide rod 80, rotation of guide rod 80 can be used to accurately determine position of drive head 22 along lead screw 28. Rotation of guide rod 80 is measured with position sensor 78, and data from position sensor 78 is fed to motor processor 64 on circuit board 66. In one embodiment, position sensor 78 includes an absolute encoder for detecting angular movement of guide rod 80.

Syringe barrel holder 24 includes front barrel clamp element 90 a and rear barrel clamp element 90 b, as shown in FIGS. 6 a-6 d. Front barrel clamp element 90 a has a curved portion 94 to hold syringe barrel 96 in position within groove 98 in rear barrel clamp element 90 b. Groove 98 of rear barrel clamp element 90 b may have different flat regions 100 a, 100 b to facilitate accommodating barrels having different diameters. Flat regions 100 c can be used to facilitate accommodating barrels having collars.

Syringe barrel holder 24 also includes barrel flange clamp 102 on the side facing drive head 22, as shown in FIGS. 6 a-6 d and 7. Barrel flange clamp 102 is for capturing barrel flange 104 in a fixed position, as shown in FIGS. 6 a-6 d and FIG. 7 so that position of drive head 22 alone determines the amount of penetration of plunger into syringe barrel 96. Syringe holder 106 includes syringe plunger holder and syringe plunger flange holder 40 and syringe barrel holder 24.

Syringe barrel holder 24 also includes barrel centering mechanism 108 for automatically centering barrel axis 110 of barrel 96 along plunger axis 54 and along center 56 of force sensor 32. Barrel centering mechanism 108 provides that both front barrel clamp element 90 a and rear barrel clamp element 90 b move equal distances in opposite directions when syringe barrel 96 is inserted, maintaining barrel axis 110 in fixed position regardless of the size of barrel 96, as shown in FIGS. 6 a-6 d.

Barrel centering mechanism 108 includes barrel racks 112 a, 112 b, as shown in FIGS. 6 a-6 d. Barrel rack 112 a is connected to front barrel clamp element 90 a and to barrel clamp sensor gear 114 located in base 116, as shown in FIG. 1. Barrel rack 112 b is connected to rear barrel clamp element 90 b and to barrel clamp sensor gear 114. Barrel sensor 76 is also connected to barrel clamp sensor gear 114, and from the magnitude of rotation it measures of barrel clamp sensor gear 114 barrel sensor 76 determines the size of syringe barrel 96. In one embodiment, barrel sensor 76 includes an absolute encoder for detecting angular movement of barrel clamp sensor gear 114. In another embodiment, barrel sensor 76 includes an absolute encoder whose angular movement provides a measure of the movement of barrel rack 112 a, as shown in FIGS. 6 b-6 d. One embodiment has a first barrel holder drive member that includes barrel rack 112 a and a second barrel holder drive member that includes barrel rack 112 b.

Spring shaft 124 carries spring 126 that provides a force against base 116 pulling front barrel clamp element 90 a toward rear barrel clamp element 90 b to apply pressure to and hold syringe barrel 96. Guide shaft 128 extends from front barrel clamp element 90 a through rear barrel clamp element 90 b and into base 116.

While the disclosed methods and systems have been shown and described in connection with illustrated embodiments, various changes may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the spirit and scope of the present invention. 

What is claimed is:
 1. A syringe infusion pump for use with a plurality of different size syringes, each different size syringe having a different syringe barrel diameter, and each of said plurality of syringes including a plunger having a plunger axis received in the barrel along a barrel axis, said pump comprising: a drive head including a force sensor positioned to sense force applied to the plunger by the drive head, the force sensor having a center; and a syringe barrel holder configured to hold each of said syringe barrels of different diameters in a fixed position with the barrel axis aligned with said force sensor center for each different diameter syringe barrel.
 2. A syringe infusion pump as recited in claim 1, further comprising a syringe plunger holder mounted on said drive head, wherein said syringe plunger holder engages the plunger with said plunger axis aligned with said force sensor center for each different diameter syringe barrel.
 3. A syringe infusion pump as recited in claim 2, wherein said syringe plunger holder comprises a first plunger holder element and a second plunger holder element, said first plunger holder element being constrained to move a distance equal to a distance moved by said second plunger holder element, but in an opposite direction.
 4. A syringe infusion pump as recited in claim 2, wherein: said drive head is configured and dimensioned to push the plunger into the barrel of each different size syringe; and said force sensor is positioned to detect force exerted by said drive head on the plunger.
 5. A syringe infusion pump as recited in claim 4, wherein said force sensor is fixed in said drive head, and said syringe plunger holder engages the plunger with the plunger axis aligned with the barrel axis.
 6. A syringe infusion pump as recited in claim 1, wherein said syringe barrel holder is configured and dimensioned to provide a fixed position for the barrel axis with respect to said force sensor center and said fixed position is independent of size of the barrel for each different diameter syringe barrel.
 7. A syringe infusion pump as recited in claim 1, wherein said syringe barrel holder includes a barrel clamp comprising a first element and a second element, said first element and said second element being movable to engage and hold a syringe barrel in said fixed position independent of the diameter of said barrel.
 8. A syringe infusion pump as recited in claim 7, wherein said first element is constrained to move a distance equal to a distance moved by said second element, but in an opposite direction.
 9. A syringe infusion pump as recited in claim 7, wherein said barrel clamp further comprises: a first rack connected to the first element and a second rack connected to the second element, said racks having opposed toothed surfaces; a gear disposed between said racks and meshing with each rack to control relative position of said first and second elements with respect to one another; and a biasing element forcing the clamp elements together.
 10. A syringe infusion pump as recited in claim 9, wherein: said barrel clamp further comprises a guide shaft secured to the first clamp element and extending through said second clamp element; and said pump further comprises a base, wherein the gear is disposed in said base and said guide shaft extends into said base.
 11. A syringe infusion pump as recited in claim 7, further comprising a barrel diameter sensor positioned and configured to detect a magnitude of separation between said first element and said second element.
 12. A syringe infusion pump as recited in claim 11, wherein said barrel diameter sensor includes an absolute encoder for detecting angular movement of said gear.
 13. A syringe infusion pump as recited in claim 2, wherein said syringe plunger holder comprises front and rear plunger clamps cooperating to position the plunger with the plunger axis aligned with the force sensor center independent of the diameter of the barrel of a syringe held in the syringe barrel holder.
 14. A syringe infusion pump as recited in claim 2, wherein said syringe barrel holder is configured to hold the barrel with the barrel axis aligned with the force sensor center in response to the syringe plunger holder positioning the plunger with the plunger axis aligned with the force sensor center.
 15. A syringe infusion pump as recited in claim 1, further comprising a processor and an alarm, wherein said force sensor is connected to provide force data to said processor, and said processor is programmed to activate said alarm if force applied exceeds a specified value.
 16. A syringe infusion pump as recited in claim 1, further comprising a drive head position sensing mechanism.
 17. A syringe infusion pump as recited in claim 16, wherein: said drive head position sensing mechanism includes a guide rod, a guide rod driver, and a guide rod sensor; said guide rod has a helical groove and said guide rod driver includes a pin that fits in said helical groove; and said guide rod sensor senses rotation of said guide rod.
 18. A syringe infusion pump as recited in claim 17, wherein said guide rod and lead screw are mounted on a base.
 19. A syringe infusion pump as recited in claim 17, wherein said helical groove extends once around said guide rod.
 20. A syringe infusion pump as recited in claim 17, wherein said guide rod sensor includes an absolute encoder for detecting angular movement of said guide rod.
 21. A syringe infusion pump for use with a plurality of different size syringes, each different size syringe having a different syringe barrel diameter, and each of said plurality of syringes including a plunger having a plunger axis received in the syringe barrel along a barrel axis, said pump comprising: a drive head configured to apply force to the plunger to operate the syringe, said drive head including a force sensor positioned to sense force applied to the plunger by the drive head, the force sensor having a center; a syringe barrel holder comprising a barrel clamp including a first clamp element and a second clamp element, said first and second clamp elements being movable to engage and hold syringe barrels of different diameters in a fixed position with the barrel axis automatically aligned with said force sensor center independent of the diameter of the barrel for each different diameter syringe barrel; and a syringe plunger holder mounted on said drive head comprising front and rear plunger clamps cooperating to automatically position the plunger with the plunger axis in alignment with the force sensor center, and with the plunger axis in alignment with the barrel axis independent of the diameter of the barrel of a syringe held in the barrel holder for each different diameter syringe barrel.
 22. A syringe infusion pump as recited in claim 21, wherein said syringe barrel holder is configured to hold the barrel with the barrel axis aligned with the force sensor center in response to the syringe plunger holder positioning the plunger with the plunger axis aligned with the force sensor center.
 23. A syringe infusion pump for use with a plurality of different size syringes, each different size syringe having a different syringe barrel diameter, and each of said plurality of syringes including a plunger with a plunger flange having a plunger axis received in the barrel along a barrel axis, said pump comprising: a drive head positioned and configured to push the plunger into the syringe barrel for each different size syringe, said drive head including a force sensor configured to sense force applied to the plunger by the drive head, said force sensor having a center; a syringe plunger holder configured and dimensioned to engage the plunger of each different size syringe with the plunger axis aligned with said force sensor center for each said different size syringe; and a syringe barrel holder configured to hold each of the syringe barrels of different diameters in a fixed position when the drive head pushes the plunger into the syringe barrel.
 24. A syringe infusion pump as recited in claim 23, wherein: said syringe plunger holder is mounted on said drive head; and said syringe plunger holder comprises a first plunger holder element and a second plunger holder element, said first plunger holder element being constrained to move a distance equal to a distance moved by said second plunger holder element, but in an opposite direction.
 25. A syringe infusion pump as recited in claim 24, wherein said first and second plunger holder elements engage the plunger with the plunger flange positioned between said elements and the force sensor, and with the plunger axis automatically centered on said force sensor.
 26. A syringe infusion pump as recited in claim 25, wherein said syringe plunger holder comprises: a first plunger holder drive member connected to said first plunger holder element; and a second plunger holder drive member connected to said second plunger holder element, said drive members providing said movement of said first element and said second element.
 27. A syringe infusion pump as recited in claim 26, wherein said first and second plunger holder drive members comprise opposite facing, spaced apart gear racks and said plunger holder further comprises a plunger holder gear disposed therebetween and mating therewith.
 28. A syringe infusion pump as recited in claim 23, wherein: said syringe barrel holder is configured and dimensioned to provide a fixed position for the barrel axis with respect to said force sensor center, said fixed position being independent of size of said barrel for each different diameter syringe barrel; and said syringe plunger holder engages each said plunger of each different size syringe with said plunger automatically axis aligned with the barrel axis of the syringe that said syringe barrel holder is holding. 